The present invention relates to a method, an apparatus, a server, and a computer program product which are capable of masking any desired partial text data in an electronic or digital document and easily changing partial text data to be masked.
Increasingly, used digital books display digital document data on a personal computer display, in for example, a viewer. Newer digital books are designed to allow editing of currently shown digital document data by replacing only desired partial text data with mask data and by tagging the partial text data. See Japanese Patent Application Publication No. 2003-173129 as a patent literature.
In contrast, to enhance a rote learning effect, a study method using conventional nondigital books has been widely used. In this method, a word to be learned by heart in a book is marked with a marker pen or the like, and a transparent color sheet is placed on the page including the marked word for filtering to prevent the word from being read. For example, a word to be learned by heart is marked with a marker pen in red, green, or the like, and the page including the marked word is filtered by a transparent color sheet in green, red, or the like. This prevents the marked word from being read.